plus who cares? Chrome OS could just be a stripped-down android, and the world would be fine. Actually I though they were already mostly the same (I have a chromebook, but no android device, I don't know what's the difference, appart from the fact that my chromebook gets regular updates)

I don't think that is correct.

There are flavors of android including vendor modified or changed specifications. They can be subtle, like a pay as you go phone carrier, or major like what Amazon has done with Fire. Each of these changes introduces security issues outside of Google's control.

With a Chromebook you get the ChromeOS from Google regardless of the vendor who made the hardware.

At least that is my understanding.

> Chrome OS could just be a stripped-down android, and the world would be fine.

Well they'd only be fine if it were equally reliable and consistent, which is not a sure bet.